Transverse cam operated station for an automatic nonsynchronous multistation assembly machine

ABSTRACT

A station for an automatic nonsynchronous multistation assembly machine operated by a cam shaft extending transversely to the line of movement of the parts in the transport system, and featuring grooved drum-type segmented cams.

United States Patent Graham et all.

[ Mar. M, 1972 TRANSVERSE CAM OPERATED STATION FOR AN AUTOMATICNONSYNCHRONOUS MULTISTATION ASSEMBLY MACHINE James T. Graham,Birmingham; Fred W. Hackstock, Sterling Heights, both of Mich.

Assignee: The Bendix Corporation Filed: Aug. 3, 1970 Appl. No.: 62,228

Inventors:

US. Cl. ..29/200 A, 29/208 C Int. Cl. B23p 19/00, B23p 19/04 Field ofSearch ..29/20O A, 208 R, 200 B, 200 P,

References Cited UNITED STATES PATENTS Re25, 86 10/1965 Cargill ..29/200A Primary Examiner-Thomas H. Eager Attorney-John R. Benefiel and Flame,Hartz, Smith and Thompson [5 7] ABSTRACT A station for an automaticnonsynchronous multistation assembly machine operated by a cam shaftextending transversely to the line of movement of the parts in thetransport system, and featuring grooved drum-type segmented cams.

14 Claims, 6 Drawing Figures ELBABBAS PMENIEUHAR 14 I972 SHEET 1 BF 4fol WNVENTORS JAMES T. GRAHAM FRED W. HACKSOCK mmsv PATENIEDMAR I 4 I972SHEET 3 BF 4 IMVENTORS JAMES W. GRAHAM FRED W MACKSTO CK PAIENIEDMAR m1912 SHEET 0F 4 FIGB INVENTORS JAMES T- GRAHAM FRED W- HACIKSTOCKTRANSVERSE CAM OPERATED STATION FOR AN AUTOMATIC NONSYNCI-IRONOUSMULTISTATION ASSEMBLY MACIIDJE BACKGROUND OF THE INVENTION 1. Field ofthe Invention This invention concerns automatic assembly machines, andmore specifically relates to nonsynchronous, multistation-type assemblymachines.

2. Description of the Prior Art In the past, multiple station automaticassembly machines were constructed with the stations interrelated toeach other by means of complex control systems. As this type of machinegrew larger and more complex, output declined because of the compoundingof downtime which results from such an interrelationship, as a stoppageat any station would discontinue activity at every station. In addition,problems of maintenance and troubleshooting were greatly aggravated.

In order to increase the size and number of stations in such machines,it was found to be necessary to disconnect the con trol systems of theindividual stations from one another, tying them together only with thepowerand free-type transport system so that each station operated as aseparate machine powered by its own individual drive system andactivated by its own control system, i.e., the nonsynchronous type ofautomatic assembly machine. The backup of parts available in this powerand free transport system act as a reservoir or cushion of parts foreach individual station, so that temporary cessations at individualstations will not affect the overall production of completed assemblies.In addition, maintenance and troubleshooting problems are greatlysimplified due to the isolation of the stations and their relativeindividual simplicity.

However, this type of machine has in the past been arranged with amultiplicity of air or hydraulic cylinders, valves, and limit switchesproviding endpoint sequential type control or by having each stationoperated with a parallel extending cam shaft either aligned with theline of movement of the parts or along side thereof. For reliability, acam system is more desirable, however, this arrangement has been limitedas to the number of cam operated motion possible in a single stationbecause the length of the cam shafts are limited by the space availablebetween adjacent stations. Additionally, complex linkages are requiredfor motions on the opposite side of the station from the cam.

Therefore, it is an object of the present invention to provide anarrangement for operating the various assembly mechanisms in which thenumber of available motions are not limited by the width of theindividual station and which permits motions on both sides of the lineof movement of the workpiece to be accomplished more easily.

SUMMARY OF THE INVENTION This and other objects which will becomeapparent upon a reading of the following specification and claims areaccomplished by providing a cam operator which extends transversely withrespect to the line of movement of the transport system.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 11 is a plan view of a multiplestation nonsynchronous automatic assembly machine.

FIG. 2 is a view taken along the section 2-2 in FIG. 1.

FIG. 3 is a view of the section taken along line 3-3 in FIG. ll.

FIG. 4 is a view of the section taken along line 4-4 in FIG. 3.

FIG. 5 is a view in partial section of the overtravel link shown in FIG.4.

FIG. 6 is a view of the section taken along the line 6-6 in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the following detaileddescription, certain specific terminology will be utilized for the sakeof clarity and a specific embodiment described in order to provide afull and clear understanding of the invention, but it is to beunderstood that the invention is not so limited and may be practiced ina variety of forms and embodiments thereof.

Referring to the drawings, and particularly FIG. I, a multistationautomatic assembly machine according to the present invention isdepicted. The machine It) includes a plurality of assembly stations 12interconnected by sections of power and free transport conveyor 14 andmay also include manual stations (not shown) for various operationswhich are better suited for manual performance.

As seen in FIG. 2, the conveyor system includes an inner and an outerroller chain l6, 18 which are continuously advanced by means ofsprockets 20 and 22 at some point in the system (FIG. I). The rollerchains 16 and I8 are supported on bars 24, 26 and carry fixed thereto ontheir upper surface portion, plates 28, 30 which serve to support andfrictionally engage a pallet 32 upon which the workpiece 34 is located.Inasmuch as the details of this system do not form a part of the presentinvention and are themselves known to those skilled in the art, it isnot felt necessary to describe this in great detail.

In operation, base members such as housings of the workpiece 34 to beassembled are placed on a pallet 32, which advances successively to eachstation 12, each of which may add parts from a supply and feed mechanism36, to the assembly or may merely manipulate elements previously mdedthereto.

Referring to FIG. 3, a station 12 with an operating mechanism accordingto the present invention is shown in some detail. This station isadapted to receive pallets 32 which are carried into the station by theroller chains 16, 18.

The station 12 includes a locating fixture 38. The pallet 32 is adaptedto be stopped andlocated with respect to the fixture 38 immediatelyafter it comes into approximate registry with the station 12, by meansof a rough stop mechanism (not shown).

At this point a series of actions take place all controlled and operatedby means of a transversely extending drum cam assembly 40 which isdriven by a motor 42, speed reducer 44 and clutch unit 45 and brake unit46, preferably pneumatically operated, which actions are initiated bysuitable controls, in order to intermittently rotate the cam assembly40.

The cam assembly 40 includes a drum member 48 which is supported bymeans of bearings 50, 52 mounted on partitions 54, 56, respectively,supported in the station base 58. Secured to the drum 48 are a pluralityof cam groove sections 60, 62, 64, 66, and 68 which may be constructedof standardized segments individually bolted or otherwise: secured tothe drum member 48. Associated with each respective segment 60, 62, 64%,66, 68 is a linkage assembly 70, 72, 74, 76, and 78 for per forming aspecific motion with regard to the workpiece or in locating or providingauxiliary support for the pallet 32. Each linkage assembly 70, 72, 7A,78 is supported by a crossmember 80 which is in turn supported bypartitions 5d, 56 as well as partition 82, while linkage assembly 76 issupported by a plate 841 in turn supported by appropriate bracketry.

Each linkage assembly 70, 72, 74, 76 and 78 includes an associated link86, 88, 90, 92 and 94 rotatably supported by pivots 96, 98, 100, 102,104. Each link 86, 88, 9t), 92, 94 has an associated cam follower I05,I07, I09, III, 1113 disposed in its respective cam groove so as toconstrain it to move in conformity with the particular contours thereof.

Each link 86, 88, 90, 92, 94 is drivingly associated with a mechanismdesigned to perform some motion function which is associated with thespecific operation to be performed at the particular station 12.

For example, link 88 is adapted to operate a wepge pin device 114 whichserves to locate the pallet and workpiece with respect to the registryfixture 38,. link 92 is adapted to drive an auxiliary support clampmechanism H6, link 88 is adapted to operate a bearing or seal feedmechanism 118, link 86 operates a bearing positioning mechanism 119,while link 94 drives a press mechanism 120, arranged to press a bearingor seal into the workpiece 34.

Inasmuch as the details of the particular motion mechanisms are not inthemselves a part of the present invention and may be any of a greatvariety of such known movements, it is not felt necessary to describethese in great detail.

Suffice it to say that each of these mechanisms are operated in asequence and in a manner determined by the particular contour of itsassociated cam groove to accomplish the intended station operation,after which time the cam drive is discontinued via a control arrangement(not shown) cooperating with the clutch unit and brake unit 46 to awaitthe next cycle.

From this description, it can be be appreciated that the space occupiedby the cam mechanism and its associated linkages occupies substantiallyless length of assembly line than a corresponding parallel disposed cammechanism. Indeed in this arrangement, the several cam operated linkagesoccupy very little more space than a single such linkage, and hence thenumber of motions available is not dependent on the line space availableand substantially more motions are possible at each station.

In addition, the cam may be located so that motions on either side ofthe line may be easily and directly taken therefrom.

As shown in FIG. 4, pivot 74, which is typical, includes a socket 122secured to crossmember and aligned with a corresponding bore 125therein, and containing a ball 124 urged to the right as viewed in FIG.4 by means of a compression spring 126. A bushing 127 may be included tolessen wear and maintain an accurate fit with the ball 124.

Disposed juxtaposed to the ball 124 is a pivot post 128 having a baseportion 130 formed with a generally dished depression 132, normallydisposed with the ball 124 centered therein. The pivot post 128 ismaintained against the crossmember 80 by means of a slotted bracket 136secured to the crossmember 80 and formed with an opening 138 so as toallow limited movement of the pivot post in the plane of its abutmentwith the crossmember 80, while preventing movement out of this plane.

The link 90 is rotatably supported on a reduced end portion 140 of thepivot post 128, and retained thereon by means of a thrust washer 142 anda pneumatic fitting 144 threadedly engaging the end portion 140.

Associated with the fitting 144 is a source of pneumatic pressure 146connected thereto via line 148, which communicates via the fitting 144with a central passage 150 formed in the pivot post member 128, leadinginto the center of the dished depression 132. The source 146 is alsoconnected via the fitting 144 and a line with a pressure switch 152which is arranged to control the clutch unit 45 and brake unit 46 bymeans of a solenoid valve 154 which is operatively connected thereto andserves to control communications of the pneumatic source 156 which inturn controls the application of the clutch 45 and brake 46 todiscontinue drum movement. The solenoid valve 154 also may serve as theprimary cycle control during normal operations.

An indicator 158 may also be operated by the pressure switch 152.

In operation, if a jam or other overload condition occurs in any one ofthe linkage assemblies as for example the linkage 74, the reaction forceat the pivot 100 will cause the associated link 90 acting through thepivot post 128 and the dished depression 132 will cause the ball 124 tobe cammed to the left as viewed in FIG. 4 against the bias of thecompression spring 126, allowing the link 90 to move away from its pivotpoint in the direction tending to relieve the overload condition.

At this point, the passage is vented since the ball 124 no longer iscentered in the depression 132 which in turn causes a pressure reductionin line 145 and pressure switch 152, which is arranged to deactivate theclutch 45 and apply the brake 46, and cease further rotation of the camassembly 40.

The indicator 158 is also activated thereby so that an operator may beapprised of the shutdown.

From this description, it can be appreciated that this arrangement issensitive to overload conditions in the individual link mechanisms andacts to immediately relieve the excessive forces as well as to shut downall further activity at the station, and hence, providing a solution tothe problem of detecting the individual jams. Furthermore, since thepivots are the locations where the excessive force levels are detected,the shifting mechanical advantage of the cam groove sections and the camfollower does affect its function, and hence this arrangement alsoeliminates this source of error.

The overload level of each link mechanism 70, 72, 74, 76, and 78 alsomay be individually tailored by controlling the bias force applied tothe ball by the compression spring and/or the ramp angle of theassociated dished depression.

As noted above, a problem has existed in accurately locating a member bymeans of cam and linkage mechanisms due to the play involved therein andthe efiects of wear. An example of this type of situation is thepositioning mechanism 119 referred to operated by the linkage 70. Thismechanism serves to receive a part 160, such as a seal or bearing fromthe feed mechanism 118, into a holding member 162, and transport it intoa proper position with respect to the workpiece 34 for emplacement bythe press mechanism 120. Thus, the holding member 162 must accurately bebrought into registry in these positions with respect to the feedmechanism 118, the press mechanism 120 and the workpiece 34.

The arrangement provided for accomplishing this includes a stationaryblock 164 fixed to the housing 58 and a pair of rods 166, 168 slidablydisposed in bores formed in the block 164. The rods 166, 168 areconnected at one end to an end plate 170 in turn connected to theholding member 162, and at the other end to end plate 172. The end plateis adapted to be driven by the link 86 by means of an overtravel link174 pinned at 176 to the link 86 and at 178 to the end plate 172.

An adjustable positive stop 188 is threaded into the end plate 170,while a cooperating adjustable positive stop 190 is similarly threadedinto the block 164. An adjustable stop 192 is threaded into end plate172 and a cooperating stop 194 is threaded into the block 164.

The overtravel link 174, as shown in more detail in FIGS. 5 and 6, isadapted to provide a resilient limited lost motion connection betweenthe link 86 and the end plate 172, and includes a pair of end rods 196and 198 adapted to be pinned to the link 86 and end plate 172,respectively. End rod 196 is threadedly connected to a rod 200,extending into a housing 202 and received into an opening 204 formed ina cup member 204. The cup member 204 is threaded to the end rod 198.

Surrounding rod 200 and disposed in the housing 202 is a compressionspring 206, bearing at one end against a shoulder 208 in the housing 202and at the other end on a compression washer 210.

Compression washer 210 is forced thereby against the end 212 of the cupmember 204, which in turn is abutting an internal shoulder 216 of a cap218 threaded on the end of the housing 202.

Movement of the rod 200 in the housing 202 is limited by means of acompression washer 220 abutting the housing end 222 and adjusting locknut 224. The compression spring 206 also acts on the rod 200 via a pairof protuberances 226 and 228 slidably received in a pair of slots 230,232, in the cup member 204, with the compression washer 210 extendinginwardly to engage the protuberances 226 and 228.

In the position shown with the cup member 204 abutting the spacer washer214 and the compression washer 220, a lost motion clearance I isprovided between the rod 200 and the cup member 204, which allowsrelative movement between the end rods 196, 198 until the rod 200 abutsthe bottom of the opening 203.

In operation, as the link 86 is pivoted in a clockwise direction asviewed in PM]. 3, the end plate 172 and connected rods H66, ll, endplate 170 and holding member 162 are stroked to the right via thedriving connection of the overtravel link R74 acting through itscompression spring 206, until the stops 188, 1190 contact each other.This point is selected to be at the precise registry point required byadjusting one or the other or both of the stops 188, 190. At this point,the cup member 204 becomes relatively fixed, and the end rod 196 (actingthrough the compression washer 220) moves against the bias of thecompression spring 206 to the right until the cam motion begins to pivotthe link 86 in the return direction. Since a lost motion clearance l isprovided, the cam motion and linkage does not need to be preciselyadjusted and maintained to begin the return motion at the precise momentwhen the stops 188 and 190 come into contact.

Upon movement of the link 86 counterclockwise, the end plate 172 isstroked by the overtravel link 17d to the left, together with theconnected rods 166, 168, end plate 170, and holding member 162 until thestops 192, 1% contact each other, at which time the cup member 204becomes fixed relative to rod 206. At that point, the rod 200 movesagainst the bias of the spring 206 acting thereon through theprotuberances 228 and 226 and the thrust washer 210 (to the left asviewed in FIG. 5) until the link 86 is caused to either stop or reverseits pivotal motion by the cam groove section 60. Since the rod 200 isfree to move relative to the cup member 204, if the contact of the stops192, 194 does not precisely coincide with this stoppage or reversal ofcounterclockwise pivotal movement the rod 200 is free to continue movingto the left as viewed in FIG. 5 until the spring 206 reaches its fullycom pressed length, and hence the registry of the holding member may beprecisely adjusted independently of the linkage motion within the limitsof this overtravel.

Additional thrust washers 210 or washers of differing thickness thereofmay be utilized, as well as springs of varying rates in order to controlthe relative stiffness of the overtravel link 174 to provide the properresponse for the particular velocities, masses, etc., involved in theparticular motion.

From the above detailed description, it can be appreciated that aparticularly advantageous station configuration for a nonsynchronousmultiple station automatic assembly machine has been provided inasmuchas the number of motions which can be utilized at any given station isnot limited by the station width and that motions on either side of theline are easily available.

What is claimed is:

l. A multistation assembly machine for assembly of workpiecescomprising:

transport means moving workpieces through said machine;

a plurality of workstations disposed along said transport means eachincluding operating means for performing operations on a workpiece, andat least one of said operating means including cam means having aplurality of camming surfaces arranged relative each other to extendtransversely to the line of movement of said workpieces through saidworkstation, whereby the number of operations performable by saidcamming surfaces at said station is not limited by the available lengthalong said transport means between said stations.

2. The assembly machine of claim ll wherein said cam means includes adrum member rotatably mounted along an axis extending transversely tothe line of movement of said workpieces.

3. The assembly machine of claim 2 wherein said cam surfaces comprise aplurality of grooves formed in said drum and wherein said operatingmeans includes linkage means and associated cam followers inserted insaid grooves.

4. The assembly machine of claim 3 wherein at least one of said linkagemeans includes a link member and a pivotal support for said link member,and further includes overload release means allowing displacement ofsaid link member relative said pivotal support in response to a pivotreaction force level corresponding to an overload condition in saidlinkage means, whereby overloads in said individual linkage means may beprevented.

5. The assembly machine of claim d wherein said operating means furtherincludes drive means for driving said drum member and control meansintermittently activating said drive means, and wherein said overloadmeans also includes deactivating means deactivating said drive means inresponse to displacement of said link member relative said pivotalsupport.

6. The assembly machine of claim 4 wherein said overload release meansincludes a ball member resiliently biased into engagement with said linkmember and wherein said link member includes a dished depressionengaging said ball member.

7. The assembly machine of claim 6 wherein said overload means furtherincludes bracket means limiting the displacement of said link memberfrom said pivotal support.

8. The assembly machine of claim 6 wherein said operating means furtherincludes drive means :for driving said drum member and control meansintermittently activating said drive means, and wherein said overloadmeans also includes deactivating means deactivating said drive means inresponse to displacement of said link member from said pivotal support,said deactivating means including fluid pressure means communicatingwith said dished depression, and means responsive to the movement ofsaid ball member out of said depression to vent said fluid pressuremeans.

9. The assembly machine of claim 7 wherein said bracket means alsoincludes means limiting movement of said link member relative said ballmember to movement in a single plane.

10. In a multistation nonsynchronous assembly machine having a transportsystem for moving workpieces between assembly stations the improvementcomprising:

means for operating said assembly stations including a cam shaft meansincluding a plurality of camming surfaces arranged relative to eachother to extend transversely to the line of movement of the workpieces,whereby the number of operations drivable by said cam shaft means is notlimited by the spacing of said stations along said transport system.

111. The machine of claim 10 wherein said cam shaft means includes adrum member having said camming surfaces formed thereon extendingtransversely to the line of movement of said workpieces.

112. The machine of claim llll wherein said cam shaft means cammingsurfaces comprise a plurality of grooved segments on said drum memberand wherein said stations include linkage and cam follower meanscooperating with respective groove segments to perform the assemblyoperations.

13. The machine of claim 12 wherein one of said linkage means drives apositioning member, and wherein said operating means also includes anovertravel link interposed between said linkage and said member, saidovertravel link comprising:

a first end rod;

a second end rod;

a housing slidably receiving said first and second end rods;

a first abutment means limiting relative movement between said housingand said first end rod; a second abutment means limiting relativemovement between said second end rod and said housing; and

resilient means drivingly connected to said housing and one of said endrods, whereby resilient. overtravel of both said end rods is provided.

M. The machine of claim 13 wherein said linkage means positions saidmember at a first and second position, and wherein said operating meansalso includes a positive stop at each of said first and second positionspositively locating said member at each of said positions.

1. A multistation assembly machine for assembly of workpiecescomprising: transport means moving workpieces through said machine; aplurality of workstations disposed along said transport means eachincluding operating means for performing operations on a workpiece, andat least one of said operating means including cam means having aplurality of camming surfaces arranged relative each other to extendtransversely to the line of movement of said workpieces through saidworkstation, whereby the number of operations performable by saidcamming surfaces at said station is not limited by the available lengthalong said transport means between said stations.
 2. The assemblymachine of claim 1 wherein said cam means includes a drum memberrotatably mounted along an axis extending tranSversely to the line ofmovement of said workpieces.
 3. The assembly machine of claim 2 whereinsaid cam surfaces comprise a plurality of grooves formed in said drumand wherein said operating means includes linkage means and associatedcam followers inserted in said grooves.
 4. The assembly machine of claim3 wherein at least one of said linkage means includes a link member anda pivotal support for said link member, and further includes overloadrelease means allowing displacement of said link member relative saidpivotal support in response to a pivot reaction force levelcorresponding to an overload condition in said linkage means, wherebyoverloads in said individual linkage means may be prevented.
 5. Theassembly machine of claim 4 wherein said operating means furtherincludes drive means for driving said drum member and control meansintermittently activating said drive means, and wherein said overloadmeans also includes deactivating means deactivating said drive means inresponse to displacement of said link member relative said pivotalsupport.
 6. The assembly machine of claim 4 wherein said overloadrelease means includes a ball member resiliently biased into engagementwith said link member and wherein said link member includes a disheddepression engaging said ball member.
 7. The assembly machine of claim 6wherein said overload means further includes bracket means limiting thedisplacement of said link member from said pivotal support.
 8. Theassembly machine of claim 6 wherein said operating means furtherincludes drive means for driving said drum member and control meansintermittently activating said drive means, and wherein said overloadmeans also includes deactivating means deactivating said drive means inresponse to displacement of said link member from said pivotal support,said deactivating means including fluid pressure means communicatingwith said dished depression, and means responsive to the movement ofsaid ball member out of said depression to vent said fluid pressuremeans.
 9. The assembly machine of claim 7 wherein said bracket meansalso includes means limiting movement of said link member relative saidball member to movement in a single plane.
 10. In a multistationnonsynchronous assembly machine having a transport system for movingworkpieces between assembly stations the improvement comprising: meansfor operating said assembly stations including a cam shaft meansincluding a plurality of camming surfaces arranged relative to eachother to extend transversely to the line of movement of the workpieces,whereby the number of operations drivable by said cam shaft means is notlimited by the spacing of said stations along said transport system. 11.The machine of claim 10 wherein said cam shaft means includes a drummember having said camming surfaces formed thereon extendingtransversely to the line of movement of said workpieces.
 12. The machineof claim 11 wherein said cam shaft means camming surfaces comprise aplurality of grooved segments on said drum member and wherein saidstations include linkage and cam follower means cooperating withrespective groove segments to perform the assembly operations.
 13. Themachine of claim 12 wherein one of said linkage means drives apositioning member, and wherein said operating means also includes anovertravel link interposed between said linkage and said member, saidovertravel link comprising: a first end rod; a second end rod; a housingslidably receiving said first and second end rods; a first abutmentmeans limiting relative movement between said housing and said first endrod; a second abutment means limiting relative movement between saidsecond end rod and said housing; and resilient means drivingly connectedto said housing and one of said end rods, whereby resilient overtravelof both said end rods is provided.
 14. The machine of claim 13 whereinsaid linkage means positions said member at a first and second position,and wherein said operating means also includes a positive stop at eachof said first and second positions positively locating said member ateach of said positions.